A newspaper ad from July 1969 informs the buying public about the ongoing enclosing renovation at the retail complex. Known, by this time, as simply MID-ISLAND PLAZA, its newly-roofed concourses will be dedicated in October 1969. 
Advert from the Stackler & Frank Company

This logo was in use by 1970...possibly introduced as part of the mall's enclosing renovation.
Graphic from the Stackler & Frank Company

In the mid-'70s, Fly By Night Audio, an electronics store, was housed in a jet airplane parked at the mall.
Photo from https://www.flickr.com / "Gregchris66"

A new mall moniker, THE PLAZA AT MID ISLAND, had been instituted by 1979.
Graphic from the Stackler & Frank Company

A site plan from the same time. The Twin North & South Theatres had been added in the mid-1960s. As mentioned above, the mall was enclosed in 1969. A second anchor, S. Klein, was also added. The store became the Korvettes seen here in 1975. By this time of this layout, the 5 & dimes and supermarkets were long gone.

PLAZA AT MID-ISLAND TENANTS 1979:

GERTZ (with Long Island Room restaurant, freestanding Tire & Auto Center and Gertz Furniture) / E.J. KORVETTE / Alarmingly Safe & Sound / American Handicrafts / Athlete's Foot / Bagel Nosh / Baldwin Piano & Organ Company / Beacon Photo / B. Dalton Bookseller / Bond Clothes / Boystown / Brassman Creations / Brooks / Budget Uniform / Buster Brown Shoes / Cardinal Cards & Gift Shop / Car-Lin Bake Shop / Carol Jewelers / Casual Corner / Chandler's Shoes / Chess King / Coleman's Formal Den / Combine Camera / Consumer Distributing / Courtesy Drugs / The Cubby Corner / Deutsch Jewelers / Dry Dock Savings Bank / Electronic City / Flagg Brothers Shoes / Florsheim Thayer McNeil Shoes / Frankel's Home Furnishings / G & G Shops / Game Room / GNC / Green Shield Optician / H & R Block / Hanover Shoes / Hardy Shoes / Hicksville Florists / Household Finance Corporation / Holiday Spa / Hurdy Gurdy / Import Alley / Jo-Ann's Nut House / K & D Photography / Keepsake Diamond Center / Kenny's restaurant / Kinney Shoes / Kisses / Lerner Shops / Long Island Bank / Long's Chinese Restaurant / Love Brothers / Kyla International / Matsu Oriental Gift Shop / Michael's / Mid-Island Key Shop / Mid-Island Liquors / Mid-Island Stridrite Shoes / Mid-Island Travel Bureau / Mister Max Pretzel / Motherhood Maternity / My M restaurant / Nathan's Hot Dogs / National Shirt Shops / National Shoes / Pants Place Plus / Pembrook China / Perfect Pretzel / Petland Discounts / Pizza d'Amore / Plaza Barber Shop / Q & A Research / Radio Shack / Record World / Select / Showboat / Sid's Pants / Singer Sewing Center / Small Wonders / Stadler Florsheim Shoes / The Ground Round restaurant / The Limited / The Magic Shop / The Material Image / The Rage Salon / The Square Tree / The Wild Pair / Thom McAn Shoes / Three For All / Tricia Boutique / Twin Theatres North & South / U.S. General / Visions of Sugar Plums / Waldenbooks / Walsh Shoe Repair / Wrangler Wranch