Lawrence B. McKay, 71, an advertising executive and former assistant publisher of the Army Times Publishing Co. who lived in Arlington for 20 years before moving to Texas in 1979, died of a heart ailment Oct. 4 at his home in Houston.

He was president of the Marketing Innovations Co., a concern he founded in Arlington in 1967 and moved to Texas in 1979.

Mr. McKay was a native of New York City and earned two bachelor's degrees and a master's degree in engineering at Columbia University. After serving in the Army in the Aleutians during World War II, he worked in advertising in New York.

He came to Washington as a marketing specialist with the old Larrabee Advertising Agency. From 1959 to 1963, he was assistant publisher of the Army Times Publishing Co. and helped establish its Register magazine, a technical journal.

Mr. McKay worked for several other advertising concerns, including Ketchum, McLeod & Grove, where he was an account executive, before founding his own company.

He had been active in George Bush's campaign effort in Texas for the 1980 Republican presidential nomination.

Survivors include his wife, Merle Reagan McKay of Houston, and two sisters, both of New York.