Trying to remember the name

[Lego Otaku]

Mid 1970s, when I was in pre-school I remember playing with giant bricks that came in red, yellow, and blue. They all looked like typical 2x4 Lego bricks but they were a lot bigger. When I could read, I remember seeing "LEGO" on each of the studs, just like a normal 2x4 brick. It is not Quatro as those had open studs and didn't come out in 70's or 60's. It is much bigger than Duplo.

AFAIK they were only available in 2x4 red, yellow, and blue. Anyone remember this and know what series it was?

[drevim]

Try Dacta Duplo. I can only find one example on Brickipedia, set number 1402, under Duplo themes. Early/mid 70s, big blocks, bright colors. I remember these as well, must have been a staple of the time.

Hope it helps.