SCHEDULE 13G  
  
Amendment No. 1  
Oregon Steel Mills Incorporated  
common stock  
Cusip # 686079104  
Filing Fee: No  
 
 
Cusip # 686079104  
Item 1:	Reporting Person - FMR Corp. - (Tax ID:  04-2507163)  
Item 4:	Commonwealth of Massachusetts  
Item 5:	None  
Item 6:	None  
Item 7:	None  
Item 8:	None  
Item 9:	None  
Item 11:	0.00%  
Item 12:	HC   
  
  
 
 
Cusip # 686079104  
Item 1:	Reporting Person - Edward C. Johnson 3d - (Tax ID:  ###-##-####)  
Item 4:	United States of America  
Item 5:	None  
Item 6:	None  
Item 7:	None  
Item 8:	None  
Item 9:	None  
Item 11:	0.00%  
Item 12:	IN   
  
  
 
 
SCHEDULE 13G - TO BE INCLUDED IN STATEMENTS  
FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)  
  
  
Item 1(a).	Name of Issuer:  
  
		Oregon Steel Mills Incorporated  
  
Item 1(b).	Name of Issuer's Principal Executive Offices:  
  
		1000 Broadway Building, Suite 2000  
		Portland, OR  97205-3074  
  
Item 2(a).	Name of Person Filing:   
  
		FMR Corp.  
  
Item 2(b).	Address or Principal Business Office or, if None, Residence:  
  
		82 Devonshire Street, Boston, Massachusetts  02109  
  
Item 2(c).	Citizenship:  
  
		Not applicable  
  
Item 2(d).	Title of Class of Securities:  
  
		Common Stock  
  
Item 2(e).	CUSIP Number:    
  
		686079104  
  
Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b) and the  
person filing, FMR Corp., is a parent holding company in accordance  
with Section 240.13d-1(b)(ii)(G).  (Note:  See Item 7).  
  
Item 4.	Ownership  
  
	(a)	Amount Beneficially Owned: 
	None  
  
	(b)	Percent of Class: 
	0.00%  
  
	(c)	Number of shares as to which such person has:    
  
	(i)	sole power to vote or to direct the vote: 
	None  
  
	(ii)	shared power to vote or to direct the vote: 
	None  
  
	(iii)	sole power to dispose or to direct the disposition of: 
	None  
  
	(iv)	shared power to dispose or to direct the disposition of: 
	None  
  
  
 
 
Item 5.	Ownership of Five Percent or Less of a Class.  
  
	If this statement is being filed to report the fact that as of  
the date hereof, the reporting person has ceased to be the  
beneficial owner of any of the class of securities, check the  
following (X).  
  
Item 6.	Ownership of More than Five Percent on Behalf of Another Person.  
  
	Not applicable.  
  
Item 7.	Identification and Classification of the Subsidiary Which Acquired  
the Security Being Reported on By the Parent Holding Company.  
  
	Not applicable.  
  
Item 8.	Identification and Classification of Members of the Group.  
  
	Not applicable.   
  
Item 9.	Notice of Dissolution of Group.  
  
	Not applicable.  
  
Item 10.	Certification.  
  
	Inasmuch as the reporting persons are no longer the beneficial  
owners of any of the number of shares outstanding, the  
reporting persons have no further reporting obligation under  
section 13(d) of the Securities and Exchange Commission  
thereunder, and the reporting persons have no obligation to  
amend this Statement if any material change occurs in the facts  
set forth herein.  
  
  
Signature  
  
	After reasonable inquiry and to the best of my knowledge and  
belief, I certify that the information set forth in this  
Schedule 13G in connection with FMR Corp's beneficial ownership  
of the common stock of Oregon Steel Mills Incorporated at  
December 31, 1994 is true, complete and correct.   
  
  
  
	February 13, 1995	  
Date  
  
  
  
	/s/Arthur S. Loring  
Signature  
  
  
  
	Arthur S. Loring, Vice  
President	  
Name/Title