In November 1981, while working at High Fidelity magazine, Oestreich served on the faculty of the Music Critics Association's summer institute in Pittsburgh held in conjunction with a three-program British music festival given by the Pittsburgh Orchestra under André Previn. He has since served as a panelist at annual conferences held by the association.
In 1983, most of the senior music critics at High Fidelity and Musical America – including Harris Goldsmith (born 1936), Dale Harris (1928-1996), Andrew Porter, Will Crutchfield, Paul Henry Lang, Allan Kozinn, Peter G. Davis (born 1936), Kenneth Furie (born 1949), David Peter Hamilton (born 1935), Robert P. Morgan (born 1934), and Conrad L. Osborne (born 1934) – resigned in protest over a reduction of autonomy for Oestreich, their music editor, who had been informed by the parent company that the classical music section was going to be reduced from an average of 18 pages per issue to 8 pages by January 1984, and further reduced to 1 or 2 pages by December 1984.
On behalf of the parent company, ABC Leisure Magazines of ABC Publishing, William Tynan explained that they were going to "blend lengthy classical features into its highly acclaimed Musical America," a slim magazine sewn into the centerfold of selected issues of High Fidelity and available only by subscription. Musical America, at the time, had a circulation of about 20,000 subscribers. High Fidelity had a circulation of nearly 400,000. Tynan said that High Fidelitys average reader "no longer prefers the lengthy classical music articles that have appeared as part of the previous format."
A year later (1984), many of those critics became the core review staff for a start-up classical record magazine Opus, with Oestreich as editor. The magazine, a bi-monthly, ran for four years. Historical Times, Inc., of Harrisburg, Pennsylvania, was the publisher. Warren B. Syer (1923-2007), who had published High Fidelity for 30 years, was president of Historical Times.
While filling in as interim editor of the Arts and Leisure section of The New York Times in September 1988, Oestreich accepted a position as program annotator for the Cleveland Orchestra. He succeeded Klaus George Roy (1924-2010), who had held the post for 30 years, and was succeeded by Peter G. Laki (born 1954), a musicologist, teacher, and singer.
Oestreich left his post with the Cleveland Orchestra in March 1989 to accept a permanent position as editor of arts and leisure for The New York Times. He served in this position until accepting a buyout offer in January 2013, reported as retirement from full-time work for the paper. He continues to contribute pieces to the Times as of October 2017.